Device for generating a plurality of plasma jets

Abstract

The invention relates to a device for generating a plurality of plasma jets (1), comprising at least one gas inlet (2), a first electrode (3), and a second electrode (4), wherein the first electrode (3) and the second electrode (4) each have a grid structure with grid bars (5) and cut-outs (6) situated between the grid bars (5A, 5B), the first electrode (3) and the second electrode (4) being parallel to one another; a cavity (7) is provided between the first electrode (3) and the second electrode (4); the electrodes (3, 4) are arranged such that a respective plasma generation point (P) is provided in the cavity (7) between each grid bar (5A) of the first electrode (3) and each grid bar (5B) of the second electrode (4); the first electrode (3) has, on the side facing the cavity (7), a first plate-shaped dielectric layer (8), and the second electrode (4) has a second dielectric layer (9) between the grid bars (5B) of the second electrode; and a respective plasma jet (1) can be generated at each plasma generation point (P). The invention thus provides a way of generating a plurality of uniform streamers and of controlling the quality of the generation process.

Description

[0001] Device for generating multiple plasma jets

[0002] The invention relates to a device for generating multiple plasma jets comprising at least one gas inlet, a first electrode and a second electrode.

[0003] Plasma is a state of matter consisting of ionized gases. It possesses high energy and can be generated at high temperatures and pressures. In some cases, plasma can be used in gas conversion to accelerate chemical reactions or produce specific products. For example, plasma can be used in the conversion of natural gas to hydrogen to increase the efficiency of the process. There are also plasma reforming processes where plasma is used to convert biomass or other carbon sources into synthesis gas. Overall, plasma can play a significant role in optimizing gas conversion processes.

[0004] One of the most promising devices in terms of effectiveness and predictable plasma properties is the dielectric barrier discharge (DBD).

[0005] Dielectric barrier discharge (DBD) reactors are a promising tool for gas conversion applications. DBD reactors are often filled with dielectric pellets, which can enhance plasma radiation when positioned in the beam path. While promising for a range of applications, their use is limited to the removal of volatile organic compounds (e.g., exhaust gases from factories, industrial plants, restaurants, etc.), air sterilization applications (e.g., surface polymerization and functionalization, etc.), nitrogen fixation (NOx, NH3), and hydrocarbon conversion (methane, CO2, or combined conversion to hydrogen, acetyl, ethane, ethylmethanol, etc.). For many such applications, energy efficiency and the efficiency of gas or pollutant conversion or removal are critical. This necessitates improved power control.

[0006] In conventional fixed-bed plasma discharge machines (PBDBDs), the pellets are filled randomly. Performance improvements are unpredictable with such random geometry. The PBDBD generates plasma jets or streamers randomly, resulting in spatial inconsistencies. The design is not robust for long-term use, is prone to clogging, and is difficult to maintain.

[0007] Pollutants and other gases to be converted have varying binding strengths. The electron energy distribution function (EEDF) in the plasma cannot be modified in conventional DBD reactors, making the removal of gases with high binding strengths, such as methane, a challenge. This necessitates the selective and controlled generation and optimization of streamers for gas removal.

[0008] Based on this, the object of the invention is to provide a way to generate a large number of uniform streamers and to control the quality of the generation.

[0009] This problem is solved by the subject matter of claim 1. Preferred embodiments are found in the dependent claims.

[0010] According to the invention, a device for generating multiple plasma jets is provided, comprising at least one gas inlet, a first electrode and a second electrode, wherein the first electrode and the second electrode each have a grid structure with grid bars and recesses arranged between the grid bars, and the first electrode and the second electrode are arranged parallel to each other, a cavity is arranged between the first electrode and the second electrode, the electrodes are arranged such that a plasma generation point is arranged in the cavity between a grid bar of the first electrode and a grid bar of the second electrode, the first electrode has a first plate-shaped dielectric layer on the side facing the cavity and the second electrode has a second dielectric layer between the grid bars, and a plasma jet can be generated at each plasma generation point.A key aspect of the invention is the grid-like design of the electrodes. This allows the generation of individual plasma jets to be restricted to specific positions. Furthermore, individual plasma jets can be amplified. The device's design enables a customized configuration of the electron energy distribution function and increases the efficiency of pollutant removal. Preferably, identical plasma jets are generated at the plasma generation points. These identical plasma jets arise from the regular pattern created by the grid-like electrodes.

[0011] In this context, the term plasma jet is understood to mean, in particular, the English term "plasma streamer", which is more common in the field of plasma technology.

[0012] The device enables the generation of a large number of, in particular, identical plasma jets or streamers, preferably for large-area processing, which is more controllable and exhibits predictable behavior.

[0013] According to a preferred embodiment of the invention, a gas inlet is arranged at each plasma generation point. Gas injection at each plasma generation point enables a uniform distribution of the gas. For efficient treatment, a more uniform distribution of the gas through the plasma region is required. This is ensured by gas injection at each of the plasma generation points.

[0014] According to a preferred embodiment of the invention, a first auxiliary dielectric, in particular in the form of several hemispheres, is arranged on the side of each grid bar of the second electrode facing the cavity. The hemisphere is preferably arranged such that its center lies at the intersection of two mutually perpendicular grid bars of the second electrode. This creates a uniform pattern. It is further preferred that the first auxiliary dielectric has the shape of a toroidal vortex. A "toroidal vortex" is understood to be the three-dimensional shape of a swirling ring that is curved towards the center, i.e., convex. This guides fluid towards the center. The toroidal vortex is arranged such that its center lies above the opening between two grid bars.In this way, the nozzle created serves to amplify the electric field at the opening and to guide the plasma jet through it. The vortex shape, and especially the convex shape of the nozzle, enhances the electric field, allowing the plasma jet to emerge from the opening between the two grid bars.

[0015] According to a preferred embodiment of the invention, at least one second auxiliary dielectric is suspended in the cavity between the first dielectric layer and the first auxiliary dielectric. It is further preferred that the second auxiliary dielectric has the shape of at least one rod aligned parallel to the electrodes and / or the shape of a sphere. "Suspended" in this context means a state in which the second auxiliary dielectric has no contact with the electrodes or other auxiliary dielectrics in any of the three spatial directions. For this purpose, supports are provided, which can be arranged, for example, at the edges of a housing. The supports hold the auxiliary dielectric. The suspended auxiliary dielectrics are used to enhance each plasma jet in the same way. Most reactive substances are generated near the dielectric surface. With this design, several identical plasma jets are generated.By positioning the auxiliary dielectrics in the path of the plasma beam in a similar manner at all positions, all plasma beams are amplified identically. If the auxiliary dielectrics or pellets were positioned arbitrarily, the plasma beams would not be amplified identically.

[0016] It is preferably provided that the second auxiliary dielectrics or dielectric particles are equipped with surface functionalities to improve the plasma-induced surface reactions as catalytic properties or to increase the interaction time of reactive radicals through adsorption. The second auxiliary dielectrics can, in particular, have the form of spheres over rods, several parallel rods, rods combined with spheres, cords, or other three-dimensional structures.

[0017] According to a preferred embodiment of the invention, two adjacent secondary auxiliary dielectrics are connected to each other via a cord. The cord can be, in particular, metallic or dielectric. The cord serves only as a means for positioning or suspending the auxiliary dielectrics. Further means for positioning or suspension are not excluded.

[0018] According to a preferred embodiment of the invention, the first dielectric layer and / or second dielectric layer and / or the first auxiliary dielectric and / or the second auxiliary dielectric comprises glass and / or ceramic and / or a polymer, such as polyethylene.

[0019] According to a preferred embodiment of the invention, the first dielectric layer and / or the second dielectric layer comprises a heater. The heater enables the heating of the first and / or second dielectric layer. Heating is often necessary to activate the catalyst. For this reason, it is inefficient to heat the entire reactor. Since the plasma is generated at specific locations and selectively enhanced by suspended beads, it is preferably also heated selectively. The heater can be, in particular, electrically or liquid-based. It is further preferred that the first dielectric layer and / or the second dielectric layer comprises a catalyst. Preferably, the heater is configured to introduce the catalyst into the cavity by heating the dielectric layer containing the catalyst. In this way, the addition of a catalyst is made possible.Simultaneously, interference between the catalyst and the plasma jets or streamers is avoided. The catalyst can disrupt the plasma jets or streamers. Since the plasma jets are generated at specific locations, the catalyst is preferably selectively charged so that interference with the plasma jets is largely avoided.

[0020] According to the invention, the use of the device described above for gas conversion is further provided for. In particular, the use of the device for gas conversion of gases that are difficult to break down, such as CO2, is provided for.

[0021] The invention will now be explained in more detail with reference to the drawings and a preferred embodiment.

[0022] In the drawings, Fig. 1 shows a device for generating plasma jets according to the

[0023] State of the art in a schematic sectional view,

[0024] Fig. 2 shows a device for generating plasma jets according to a preferred embodiment of the invention in a schematic sectional view.

[0025] Figure 1 schematically shows a device for generating plasma jets according to the prior art. Two parallel electrodes 3, 4 enclose a cavity 7 in which several plasma generation points P are located. A dielectric layer 8, 9 is arranged on each of the electrodes 3, 4. Plasma jets 1 are generated at the plasma generation points P. With this arrangement, arbitrary and different plasma jets or streamers are generated. This results in spatial irregularities.

[0026] In contrast, Fig. 2 schematically shows a device for generating plasma jets according to a preferred embodiment of the invention. The device comprises a first electrode 3 and a second electrode 4, both of which are lattice-shaped and arranged parallel to each other. Both electrodes 3, 4 have several lattice bars 5A, 5B, between which recesses 6 are provided. A cavity 7 is arranged between the electrodes 3, 4, in which the plasma jets 1 are generated. The first electrode 3 is covered with a first dielectric layer 8. The second electrode 4 is arranged in a second dielectric layer 9. A plasma generation point P is located between a lattice bar 5A of the first electrode 3 and the opposite lattice bar 5B of the second electrode 4. A gas inlet 2 is arranged at each plasma generation point P.The first electrode 3 is the powered electrode, while the second electrode 4 is the grounded electrode. At each intersection of the grid bars 5B of the second electrode 4, a first auxiliary dielectric 10 in the form of a hemisphere is arranged. This first auxiliary dielectric 10 can control the direction of movement of the plasma jet 1. In the cavity between the grid bars 5A of the first electrode 3 and the grid bars 5B of the second electrode 4, second auxiliary dielectrics in the form of pellets are suspended. As shown in Fig. 2, the second auxiliary dielectrics can have the form of one or more rods, a sphere, or a rod in combination with a sphere. Fig. 2 also shows that two adjacent spherical second auxiliary dielectrics 11 are connected to each other by a cord 13.

[0027] Due to the grid-like electrodes, repulsions between adjacent plasma jets or streamers can be avoided. The suspended secondary auxiliary dielectrics enable the uniform improvement of the plasma jet 1 to achieve a homogeneous distribution.

[0028] The first dielectric layer 8 includes a heater 12 and contains a catalyst charge. Heating the catalyst charge ensures the addition of the catalyst without causing interference between the catalyst and the plasma jets 1.

[0029] Reference symbol list

[0030] 1 Plasma jet

[0031] 2 Gas inlet 3 First electrode

[0032] 4 second electrode

[0033] 5A Grid rod of the first electrode

[0034] 5B Grid rod of the second electrode

[0035] 6 Recess 7 Cavity

[0036] 8 first dielectric layer

[0037] 9 second dielectric layer

[0038] 10 first auxiliary dielectric

[0039] 11 Second auxiliary dielectric 12 Heating

[0040] 13 string

[0041] P Plasma generation point

Claims

Patent claims 1. Device for generating multiple plasma jets (1) comprising at least one gas inlet (2), a first electrode (3) and a second electrode (4), wherein the first electrode (3) and the second electrode (4) each have a grid structure with grid bars (5) and recesses arranged between the grid bars (5A, 5B). (6) and the first electrode (3) and the second electrode (4) are arranged parallel to each other, with a cavity between the first electrode (3) and the second electrode (4). (7) is arranged, the electrodes (3, 4) are arranged such that a plasma generation point (P) is arranged in the cavity (7) between a grid bar (5A) of the first electrode (3) and a grid bar (5B) of the second electrode (4), the first electrode (3) has a first plate-shaped dielectric layer (8) on the side facing the cavity (7) and the second electrode (4) has a second dielectric layer (9) between the grid bars (5B) of the second electrode, and a plasma jet (1) can be generated at each plasma generation point (P).

2. Device according to claim 1, wherein a gas inlet (2) is arranged at each plasma generation point (P).

3. Device according to one of the preceding claims, wherein a first auxiliary dielectric (10), in particular in the form of several hemispheres, is arranged on each grid rod of the second electrode on the side facing the cavity.

4. Device according to one of the preceding claims, wherein at least one second auxiliary dielectric (11) is arranged suspended in the cavity (7) between the first dielectric layer (8) and the first auxiliary dielectric (10).

5. Device according to one of the preceding claims, wherein the second auxiliary dielectric (11) has the shape of at least one rod aligned parallel to the electrodes (3, 4) and / or the shape of a sphere.

6. Device according to one of the preceding claims, wherein two adjacent second auxiliary dielectrics (11) are connected to each other via a cord.

7. Device according to one of the preceding claims, wherein the first dielectric layer (6) and / or second dielectric layer (7) and / or the first auxiliary dielectric (10) and / or the second auxiliary dielectric comprises glass and / or ceramic and / or a polymer.

8. Device according to one of the preceding claims, wherein the first dielectric layer (8) and / or the second dielectric layer (9) comprises a heater (12).

9. Device according to one of the preceding claims, wherein the first dielectric layer (8) and / or the second dielectric layer (9) comprises a catalyst.

10. Use of a device according to any of the preceding claims for gas conversion.

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